Java Executor Service waiting for all tasks to complete

Question

I am using executor service to run my 10 tasks with 2 tasks at a time.

ExecutorService executor = Executors.newFixedThreadPool(2);
for (int i = 0; i < 10; i++) {
    String name = "NamePrinter " + i;
    Runnable runner = new TaskPrint(name, 1000);
    System.out.println("Adding: " + name + " / " + 1000);
    executor.execute(runner);
}

How can I wait for all tasks to complete

https://stackoverflow.com/questions/19348248/waiting-on-a-list-of-future — Pooya, May 07 '18 at 18:27
Yes, I saw the question, but adding this line stopped the program immediately taskExecutor.shutdown(); try { taskExecutor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS); } catch (InterruptedException e) { ... } also, I don't know to tell max wait time — Jobs, May 07 '18 at 18:32
Then put up a [mcve]. But I am guessing that you call that method inside your loop?! — GhostCat, May 07 '18 at 18:34
https://stackoverflow.com/questions/19348248/waiting-on-a-list-of-future The taskExecutor.shutdown(); in the answer is stopping the program. I don't know why 300 + people upvoted the answer — Jobs, May 07 '18 at 18:44

Mạnh Quyết Nguyễn · Answer 1 · 2018-05-07T18:35:35.770

3

Use java 8 CompleteableFuture with join method to wait:

ExecutorService executor = Executors.newFixedThreadPool(2);
CompletableFuture[] futures = new CompletableFuture[10];
for (int i = 0; i < 10; i++) {
    String name = "NamePrinter " + i;
    Runnable runner = new TaskPrint(name, 1000);
    System.out.println("Adding: " + name + " / " + 1000);
    futures[i] =  CompletableFuture.runAsync(runner, executor);

}
CompletableFuture.allOf(futures).join(); // THis will wait until all future ready.

edited May 07 '18 at 18:35

answered May 07 '18 at 18:32

Mạnh Quyết Nguyễn

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Doesnt answer how to do it with an Executor Service. – GhostCat May 07 '18 at 18:35
CompletableFuture will be backed by an ExecutorService, see my edited answer – Mạnh Quyết Nguyễn May 07 '18 at 18:37

score 0 · Answer 2 · answered May 07 '18 at 18:32

Assign your callables to futures and check that you can get results from each future.

        Future future = workerExecutor.submit(new Callable() {
            @Override
            public Object call() throws Exception {
                try {
                    System.out.println("MyItemTree.TimedRunnable");
                    ReturnInterface returnInterface = (ReturnInterface) commandInterface.call();
                    returnInterface.submitResult();
                } catch (Exception ex) {
                    ex.printStackTrace();
                    throw new RuntimeException(ex);
                }
                return null;
            }
        });

        try {
            Object get = future.get();
        } catch (InterruptedException | ExecutionException ex) {
            Throwable cause = ex.getCause();

            ex.printStackTrace();
            cause.printStackTrace();
            Throwable cause1 = cause.getCause();

            if (cause1 instanceof CommandInterfaceException) {
                System.out.println("[MyItemTree].scheduleTask Cause 1= COMMANDINTERFACE EXCEPTION");
                this.componentInterface.getAlertList().addAlert(((CommandInterfaceException) cause1).getResolverFormInterface());
            }
        }

    }

The executor service itself doesn't have that simple solution for it? — Jobs, May 07 '18 at 18:38

Java Executor Service waiting for all tasks to complete

2 Answers2